In general, an autonomous mobile apparatus is used inside a block of a hull in order to carry out tasks such as welding, cutting, etc. automatically. The autonomous mobile apparatus is operated in such a way that a robot-mountable platform moves inside the block of the hull by use of a plurality of wires.
Here, a winch installed in the platform repeatedly winds and unwinds the wire that is coupled with an inner wall of the block of the hull so that the platform can move freely inside the block of the hull. Furthermore, the length of the wire that is wound and unwound by the winch needs to be precisely controlled in order to move the platform to a desired position inside the block of the hull.
However, in the commonly-used winch, if the a wire drum constituting the winch rotates in a direction of unwinding the wire while the wire does not have tension, the wire between the wire drum and a wire outlet sags or becomes loosened.
Such a loosened wire becomes either tangled of disheveled. If the winch winds the wire in this state, the wire becomes wound on the wire drum in the tangled or disheveled state. Therefore, it has been difficult to precisely control the length of the wire that is wound or unwound by the winch.
Moreover, in the commonly-used winch, if the wire drum constituting the winch rotates in a direction of unwinding the wire while the wire does not have tension, the wire that is tightly wound on the wire drum becomes loosened and separated from an external circumferential surface of the wire drum.
It is difficult to wind the wire back on the wire drum while the wire is loosened and separated on the wire drum. Therefore, it has been difficult to precisely control the length of the wire that is wound or unwound by the winch.